1. Field of the Invention
The present invention relates generally to a display, and more particularly to an optical display module having an apparatus to fix the circuit board.
2. Description of the Related Art
FIG. 1 shows parts of a conventional optical display module, which has a plastic frame 1, a twin adhesive tape 2, a printed circuit board 3 and a metal frame 4. A panel 5 is rested on the plastic frame 1, and the printed circuit board 3 is attached on the plastic frame 1 by the twin adhesive tape 2. The metal frame 4 is covered on the plastic frame 1. The metal frame 4 has a plate 4a on which a tin paste layer 4b is provided to be fixed to a back side of the printed circuit board 3 by welding, referring to FIG. 2 and FIG. 3.
The twin adhesive tape 2 is sensitive to environment, such as heat makes the adhesive of the tape molten and flowing, cold makes the adhesive solidified, and moisture makes the adhesive deteriorated. These conditions cause the twin adhesive tape 2 can not bond the printed circuit board 3 on the plastic frame 1 firmly, so that the twin adhesive tape 2 is not a well element to bond the printed circuit board 3.
The metal frame 4 has functions of protecting the plastic frame 1 and electrostatic discharge. In view of durability, the metal frame 4 usually is made of stainless with a specific surface treatment. Such metal frame 4 is hard for the tin paste bonded on it, so called “false welding”. Operator has to coated more tin paste to make sure that the printed circuit board 3 is bonded on the metal frame 4 firmly. That makes the welding process harder.
FIG. 4 shows another conventional optical display module. A plastic frame 6 has plural hooks 6a at a margin thereof, and a circuit board 7 has plural slots 7a to be engaged with the hooks 6a respectively. Such structure has no twin adhesive tape involved. But in practice, the hooks 6a will be interfered with other elements.